Fuel System Issues:
* Idle Air Control (IAC) Valve: This valve regulates air flow at idle. A dirty, sticking, or faulty IAC valve can cause erratic idle and stalling. Cleaning it (with appropriate cleaner) is often the first step. Replacement might be necessary.
* Fuel Pressure Regulator: This regulates fuel pressure in the system. A malfunctioning regulator can lead to inconsistent fuel delivery, causing stalling at idle.
* Fuel Pump: A weak or failing fuel pump may not supply enough fuel at idle, resulting in stalling. This is less likely if the car runs fine under acceleration.
* Fuel Filter: A clogged fuel filter restricts fuel flow, causing similar symptoms to a weak fuel pump.
* Dirty Injectors: Clogged or dirty fuel injectors can lead to poor fuel delivery at idle. Cleaning or replacing them might be necessary.
Ignition System Issues:
* Distributor Cap and Rotor: Worn or cracked distributor caps and rotors can cause misfires, leading to stalling, especially at idle. Inspect them for cracks, arcing, or wear.
* Spark Plug Wires: Damaged or loose spark plug wires can cause misfires and stalling. Check for cracks, fraying, or loose connections.
* Spark Plugs: Worn or fouled spark plugs can prevent proper combustion at idle. Replace them if they're old or show signs of fouling.
* Ignition Coil: A faulty ignition coil can prevent sufficient spark, resulting in stalling.
Vacuum Leaks:
* Vacuum Hoses: Cracked, loose, or disconnected vacuum hoses can disrupt the engine's idle control system. Inspect all vacuum hoses for damage.
* Intake Manifold Gasket: A leak in the intake manifold gasket can draw in unmetered air, disrupting the air/fuel mixture and causing idle problems.
Other Potential Issues:
* Throttle Position Sensor (TPS): A faulty TPS sends incorrect information to the computer, affecting the fuel/air mixture.
* Mass Airflow Sensor (MAF) Sensor: Similar to the TPS, a faulty MAF sensor can provide inaccurate readings, disrupting the idle.
* Computer Issues: Though less common, a problem with the engine control module (ECM) could cause irregular idle. This is usually diagnosed by a mechanic.
Troubleshooting Steps:
1. Check for obvious vacuum leaks: Listen carefully around the intake manifold and vacuum hoses with the engine running. You might hear a hissing sound indicating a leak. Spray carb cleaner (carefully!) around suspected areas; a change in idle speed indicates a leak.
2. Inspect the distributor cap and rotor, spark plug wires, and spark plugs: Look for visible damage or wear.
3. Clean the IAC valve: This is a relatively easy and inexpensive first step. Consult a repair manual for proper procedure.
4. Check the fuel pressure: This requires a fuel pressure gauge. Low pressure indicates a problem with the fuel pump, fuel filter, or regulator.
Recommendation:
If you're not comfortable working on your car, it's best to take it to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and make the necessary repairs. Attempting to fix complex issues without experience can lead to further damage. Providing the mechanic with the symptoms (stalling at idle) will help them focus their diagnostics.
